1. Field
The present invention relates to an improved anaesthetic scavenging face mask and more particularly, to an improved anaesthetic mask having a scavenging channel formed along the perimeter of the respiratory chamber.
2. State of the Art
Anaesthetic gases have been used on medical and dental patients advantageously for years. For example, U.S. Pat. No. 2,254,854 (O'Connell), discloses a face mask having two anaesthetic gas supply inlets and an outlet valve which allows exhaled gases to be vented into the operating room.
It has become apparent that the escape of anaesthetic gases into the operating room may have deleterious health effects. For example, there may be a tendency for the dentist, doctor or other medical personnel to become anaesthetized. Also, studies have shown that exposure to the commonly used anaesthetic gas nitrous oxide may increase the risk of certain serious diseases. Exposure of nitrous oxide to pregnant personnel may also involve an increased rate of spontaneous abortion or a higher incidence of birth defects.
Various patents disclose devices which attempt to deal with the problem of anaesthetic gases in the operating room. For example, U.S. Pat. No. 3,721,239 (Myers) discloses a suction driven exhaust system which draws off anaesthetic gases from the pop-off or vent valve of the air suction system. This patent, therefore, deals with problems of escaping anaesthetic gases remote from the face mask. U.S. Pat. No. 3,877,691 (Foster) discloses an arcuate barrier or shield having a plurality of holes on the underside. The shield acts as a barrier between the patient and the medical practitioner, and the plurality of holes are connected to a vacuum source to vent exhaled gases to a remote location.
U.S. Pat. No. 4,015,598 (Brown) discloses an anaesthetic system utilizing a double-wall mask. A vacuum source is connected to the space between the interior and exterior wall of the anaesthetic mask. The space along the rim of the mask between the inner and outer wall scavenges leaking gases. Brown also discloses a transparent mask. U.S. Pat. No. 4,219,020 (Czajka) discloses a scavenger valve attachment. This attachment is mounted on a typical anaesthetic face mask in place of a conventional exhalation valve, and includes a vacuum chamber having an annular aperture, or one or more small apertures, formed in a pair of substantially frustoconically shaped members which radiate outward from the valve body and which are spaced apart from each other to define an annular exhaust chamber.
U.S. Pat. No. 4,265,239 (Fischer, Jr. et al.) discloses a gas scavenging exhaust system which includes a peripheral exhaust chamber, which, similar to Brown U.S. Pat. No. 4,015,598, is shown to be a space between an inner and outer wall of the mask. Between the inner and outer wall are bumps which act as a spacer means to keep the peripheral exhaust chamber from collapsing under the influence of the vacuum. U.S. Pat. No. 4,312,339 (Thompson, Sr.) discloses a mask with a pair of suction nozzles which scavenge gas escaping from the mask. These nozzles are illustrated as terminating on the sides of the mask in front of the inlet and outlet tubes.
U.S. Pat. No. 4,151,843 (Brekke) discloses two separate embodiments of a nose mask. One embodiment includes a mask having an interior cavity and a pair of nasal cannulas attached to the gas flow control. Anaesthetic and exhaust gases pass from the flow control to the cannulas and vice versa through a hollow space in the mask. The second embodiment has two tubes, each of which has a compressible cuff on the nostril end for the purpose of forming a positive seal between the patient's nostril and the tube. U.S. Pat. No. 4,248,218 (Fischer) discloses a nose piece with a pair of tubes for connection to a patient's nostrils. The outer nose piece scavenges anaesthetic exhaust gases exhaled from the patient's nostrils or escaping from the tubes. The nose piece also has a plurality of holes on the underside to scavenge gases exhaled from the patient's mouth. The nose piece has a single gas supply tube and a single vacuum supply tube.
Also known are systems having on-demand gas supply, and vacuum systems which become operative to the interior of the face mask only upon exhalation of the patient, and which, nevertheless, maintain a continuous vacuum supply to the scavenging function of the mask. Also existent are systems having a slight suction effect within the respiration chamber of the mask which tends to hold the mask against the face to maintain the integrity of the seal between the mask and the face.